1. Field of the Invention
The invention relates to an automatic sheet feeder, and more particularly to a duplex/simplex automatic sheet feeder.
2. Description of the Related Art
The duplex scanners may be classified into two kinds: a first kind of duplex scanner having two scanning modules for scanning a document, and a second kind of duplex scanner having a single scanning module for scanning the document. In the first kind of duplex scanner, there is only one sheet-feeding path, and the two scanning modules respectively scan the two sides of the document on the feeding path. However, because the cost of the scanning module is high, the price of the first kind of duplex scanner is high.
In a second kind of duplex scanner, there are two sheet-feeding paths. The arrangement order of a stack of sheets or documents after being scanned has to be the same as that before being scanned in order to omit the step of rearranging the documents manually. Therefore, the documents have to be turned over three times so that the order of the stack of documents is kept unchanged.
FIG. 1 is a schematic illustration showing a conventional duplex scanning apparatus. As shown in FIG. 1, the duplex scanning apparatus includes a duplex sheet feeder 101 and a scanner 190. The scanner 190 includes a housing 191, a glass platen 192, a guiding rod 193 and a scanning module 194. The scanning module 194 may be moved back and forth along the guiding rod 193 such that the duplex scanning apparatus may perform the flatbed scan operation and the duplex sheet-fed scan operation. The duplex sheet feeder 101 includes a sheet input tray 110, a sheet output tray 120, a first sheet-feeding path 130, a temporary tray 141, a first sheet-feeding mechanism 150, and a second sheet-feeding path 160.
A plurality of sheets to be scanned is placed and stored in the sheet input tray 110, and the sheets are placed and stored in the sheet output tray 120 after being scanned. The first sheet-feeding path 130 includes a scanning region 131, a first guiding rod 132 and a second guiding rod 133. When the sheet P is being moved across the scanning region 131, the scanning module 194 under the scanning region 131 may scan the sheet.
The first guiding rod 132 guides the sheet from the first sheet-feeding path 130 to the sheet output tray 120 or the temporary tray 141. The second guiding rod 133 guides the sheet from the temporary tray 141 to the second sheet-feeding path 160, and also guides the sheet from the first sheet-feeding path 130 to the temporary tray 141. The first sheet-feeding mechanism 150 includes a pickup roller 151 and a plurality of auxiliary rollers 152, 153 and 154.
When the duplex scan process is performed, the pickup roller 151 feeds the sheet P into the first sheet-feeding path 130, the auxiliary roller 152 assists in feeding the sheet P across the scanning region 131, and the scanning module 194 scans a front side image of the sheet. Next, the auxiliary rollers 153 and 154, the first guiding rod 132, and the second guiding rod 133 cooperate to transfer the sheet P to the temporary tray 141. Then, two auxiliary rollers 154 are rotated reversely, and the second guiding rod 133 rotates in the clockwise direction so as to feed the sheet into the second sheet-feeding path 160. Next, the sheet enters the first sheet-feeding path 130 from the second sheet-feeding path 160, and is being moved across the scanning region 131, in which the scanning module 194 scans the backside image of the sheet. Thereafter, the sheet P enters the temporary tray 141 again, and is then fed into the second sheet-feeding path 160 and the first sheet-feeding path 130. Finally, the first guiding rod 132 rotates in the clockwise direction so as to transfer the sheet P to the sheet output tray 120. Consequently, the sheet P has to be turned over three time. That is, the sheet P has to be moved across the scanning region 131 thee times.
Hence, when the duplex scan operation is performed, the sheet P has to be turned over three times, and the scan time is thus lengthened. When the simplex scan operation is performed, the sheet P still has to be turned over three times such that the arranged order of the stack of sheets remains intact.
Taiwan Patent Publication No. 526865 discloses a duplex ADF (Automatic Document Feeder), which, however, has the drawback in that the arranged order of the sheets after the duplex scan processes has to be rearranged. This is problematic in a duplex ADF because the user does not wish to spend time to rearrange the sheets or documents manually.
Taiwan Patent Publication No. 529620 discloses another duplex ADF, which, however, has the drawback in that the sheet-feeding mode for the duplex scan process still has to be used when the simplex scan process is performed. Thus, the time still cannot be saved when the simplex scan process is performed.
Consequently, it is advantageous to the users if a simplex/duplex scanning apparatus, which is capable of performing the simplex/duplex scan process and keeping the arranged order of the sheets after the simplex and duplex scan processes are performed, is provided.